There are these types of brushless motors.
Brushless DC motors, with their advantages of high efficiency, low noise, and long lifespan, have permeated various fields of production and daily life. Unlike traditional brushed motors, they enhance performance through electronic commutation and are not a single category. Based on structural differences, the three most fundamental types are interior rotor, exterior rotor, and coreless brushless motors, each with its own strengths and weaknesses, and suitable for distinctly different applications.
Internal rotor brushless motor: High-speed and high-efficiency power powerhouse
The core structure is "rotor inside, stator outside," with the rotor composed of permanent magnets and the stator coils receiving periodically alternating DC current (simulating the effect of an alternating magnetic field) via a controller to generate a rotating magnetic field that drives the rotor. Advantages include high speed (up to tens of thousands of RPM), fast response, high efficiency (over 85%), compact structure, and low energy loss; disadvantages are relatively small torque, requiring a reducer under high-load conditions.
In applications, the drive systems of new energy vehicles, household air conditioner compressors, electric tools (drills, cutting machines), and computer hard disk drives all rely on their high-speed and high-efficiency characteristics.
External rotor brushless motor: The reliable choice for high torque
The structure features a "stator-centered, rotor-enclosed" design, with a larger rotor rotation radius, delivering greater torque under the same conditions. The stator coils also receive alternating-direction DC input from the controller, generating a rotating magnetic field. Advantages include high torque, smooth operation, strong load fluctuation resistance, and the ability to achieve low-speed output without an additional reducer. Disadvantages are mostly lower operating speeds (with UAV motors being an exception), slower startup and speed adjustment response, and relatively large size.
Drone propellers, elevator door mechanisms, escalator drives, and large industrial fans are all typical application scenarios, with the core requirement being stable high torque.
Coreless brushless motor: A miniature precision energy pioneer
The rotor is a coreless hollow-cup coil wound around the exterior of a permanent magnet stator. The interaction between the stator's magnetic field and the directionally controllable DC current in the rotor coil drives rotation. Advantages include compact size, lightweight, extremely high efficiency (over 95%), no electromagnetic noise, and millisecond-level response time. Disadvantages are low torque, limited power output, and higher cost.
